Knife sharpening mechanism



April 30, 1957 Filed Jan. 18. 1955 F. G. CLARK KNIFE SHARPENINGMECHANISM 2 Sheets-Sheet 1 INVENTOR.

April 30, 1957 F. s. CLARK 2,790,235

KNIFE SHARPENING MECHANISM 2 Sheets-Sheet 2 Filed Jan. 18, 1955 VENTOR.

United States Patent KNIFE SHARPENING MECHANISM Frederick G. Clark,Bnlfalo, N. Y., assignor to Eastman Machine Company, Buffalo, N. Y.

Application January 18, 1955, Serial No. 482,527

Claims. (Cl. 30-139).

This invention relates to improvements in knife sharpening mechanismsfor cutting machines of the type commonly used for cutting cloth andother sheet materials and in which the cutting is effected by areciprocatory knife, such as disclosed in Patent No. 2,563,921 datedAug. 14, 1951.

Grinders of knife sharpening mechanisms, normally move in a directionaway from the leading edge of the knife and in doing so they have atendency to pull the grinder carriage toward the back of the knife. Whenthe grinder carraige moves downwardly, the supports for the carriageextend more and more away from their bearings and as they approach thebottom of the knife they provide increasingly less support againstmovement of the carriage toward the back of the knife, and consequently,yield to the pull of the grinders on the knife. As a result of thisdeflection of the carriage from its vertical movement, the knife isground to a greater extent at the lower portion thereof than at otherportions, and consequently, knives frequently have to be discarded longbefore the upper portions of the knives have been ground down to a pointat which discarding becomes necessary.

One of the objects of this invention, consequently, is to providesupporting means for enabling the grinder carriage to move throughoutits stroke without substantial deflection from its path of movementparallel to the knife. It is also an object to provide a mounting forthe grinder carriage which is capable of successfully resisting force onthe carriage resulting from the action of the grinding elements of theknife.

The only rigid part of the machine in the vicinity of the grinders isthe upright column or standard which supports the machine from its base.This standard is made of tear-drop cross sectional shape and is made asnarrowand thin as is practical from a strength stand point so as tooffer the least resistance when guided through a lay of material in backof a cut. Grooves, slots or projections which would normally be used forguiding the grinder carriage in its movement are not practical on astandard of this type because they would either reduce the cross sectionand weaken the standard or in the case of a projection they would causeadded resistance in going through the material. A further object of thisinvention, consequently, is to provide guide means for the grindercarriage by means of which the same may be supported from the uprightcolumn or standard of the machine. A further object is to provideimproved means for guiding the grinder carriage on the column orstandard of the machine in such a manner that there will be no scoringor scratching of this standard and that no change is required on thestandard.

Other objects and advantages will be apparent from the followingdescription of one embodiment of the invention and the novel featureswill be particularly pointed out hereinafter -in connection with'th'eappended claims.

In the accompanying drawings:

Fig. 1 is a side elevation, partly broken away, of a" cloth cuttingmachine provided with knife sharpening mechanism embodying thisinvention.

Fig. 2 is a side view of a knife which has been im- Fig. 4 is afragmentary transverse sectional elevation,

thereof, on line 4-4, Fig. 3. a

Fig. 5 is a fragmentary sectional view, on line 5-5, Fig. 3.

I have illustrated in the accompanying drawings my improvements asapplied by way of example to a cut ting machine similar to the one shownin said Patent #2563921. This machine comprises the usual base 20adapted to rest on and to be moved about on a table which supports thelay of material to be cut. An upright, slender standard 21 is rigidlysecured on the base and rises upwardly therefrom and supports thestationary frame 22 of an electric motor which reciprocates the knife 23in a vertical guide at the front of the standard 21 through suitabledriving mechanism (not shown). 25 represents the usual presser footarranged on the lower end of a guide bar 27 which extends vertically infront of the knife and is suitably mountedfor vertical adjustment on themachine to set the presser foot at different levels according to thethickness of different lays or piles of material. I

The knife in the particular machine illustrated in the drawings issharpened by grinding means comprising two narrow abrasive bands orbelts 30 and 31 which are disposed at opposite sides of the knife totravel crosswise of the same in contact with the opposite sides .of

drive pulleys 32 and33 and rear spring-pressed belt tensioning pulleys34 and 35 in the direction indicated by the arrows 37, Fig. 3. Thesebelts are power-driven by the knife-operating motor and are mounted onthe underside of a grinder carriage 36 arranged to move up and downlengthwise of the knife edge to enable the belts to sharpen the knifeedge throughout its full length. This carriage 36 together with thevarious parts mounted thereon is movable vertically relatively to ahousing or cover piece 38 which is removably secured in place on themotor frame 22 at the front of the machine and encloses parts of theknife operating and sharpening mechanisms. The grinder carriage may bemounted and guided in its up and down movements in any suitable ordesired manner, for example, asdisclosed in said Patent #2563; 921 andan earlier Patent #2,183,786 issued Dec. 19, 1939 to Eastman MachineCompany, assignee. While the sharpening mechanism illustrated in thedrawings includes flexible belt grinding means, the invention is notlimited thereto, since other suitable grinding elements may be employed,if desired, and'any suitable drive mechanism for the grinding belt mayalso be employed.

In the construction illustrated by way of example, the drive pulleys 32and 33 are fixed on the lower 'ends of two vertical shafts 4t and 41which are rotatable and held against axial movement relatively to thecarriage 36:

Patented Apr..30,

having crossing right and left'hand threads and which is suitablyrot'ated through gearing shown in broken lines in Fig. 3, connecting thescrew shaft with the shaft 41, as in the patents hereinbefore mentioned.Asthe screw shaft isrptated, it moves downwardly with the grindercarriage until this carriage arrivesat the bottom of its stroke,whereupon the screw shaft again moves upwardly with the carriage.- Thedriving shafts 4i) and 41 for the belts also move downwardly with thecarriage while rotated, and during this movement the carriage is alsoguided by its sliding contact with the presser foot guide bar 27 throughthe medium of a block 43 secured to the grinder-carriage. Consequently,as the grinder carriage approaches the lower end of its stroke, thebearings of the shafts 49,41 and 44 and the presser foot bar providecreasingly less support against lateral movement of the carriage. .Thegrinder. carriage, consequently, is deflected toward the knife near thelower end of its path of move ment because of the force exerted on thegrinder carriage by the frictional contact of the grinder belts with theknife. In the past, this has resulted in the grinding of the knivesapproximately into the shape shown in Fig. 2, in which the knife has thelower portion thereof ground away on a curvature, as shown at 45 in Fig.2. Because of this curvature in the front or cutting edge of the knife,it is necessary to discard these knives long before the upper portionsthereof are worn out, thus adding to the expense of operating thecutting machine.

In accordance with this invention, I have provided means for guiding thegrinder carriage along the converging front faces of the standard orcolumn 21 of the machine, without providing on these surfaces anygrooves or outwardly extending projections which would interfere withthe passage of the standard through the cut portions of the material.For this purpose, I have provided a pair of rollers 50 which are mountedon the carriage in position to engage the converging faces of thestandard. These rollers may be of any suitable construction and areprovided with resilient or yielding surfaces to bear against theconverging faces of the standard without cutting or marring thesesurfaces. For this purpose, in the construction illustrated, I haveprovided the rollers with rings 51 of a rubber or rubber-dike material.These rings may, for example, be the well-known O-rings which are seatedin grooves formed in the rollers t These rollers may be mounted on thegrinder carriage in any suitable manner. In the construction shown, forexample, these rollers are mounted on pivoted arms 52 made of strips ofmetal having downwardly extending integral lugs 54 provided withapertures in which the roll- 2 ers are journalled. These arms arepreferably pivotally mounted on the grinder carriage, and for thispurpose, areiprovided with apertures which bear on cylindrical portions56 of bolts 57 extending through slots 53 in the grinder carriage 36.The enlarged portion 56 of each bolt straddles the slot 58 so that thebolt 5'7 may be locked in any desired position in the slot 58 by meansof a nut til)v The bolts, consequently, serve the dual purpose offorming pivots for the arms 52 and also for adjusting the pivotal-axesabout which the arms swing so that the rollers 50 will properly engagewith the converging faces of the. standard.

The rollers are preferably yieldingly urged into engagement with theconverging surfaces of the standard, and for this purpose, springs 61are provided which are arranged in holes drilled in the grinder carriage36. One end of each spring bears against a pivoted arm 52 and the otherend bears against a screw plug 62 having a threaded engagement in thehole in which the spring is located. Consequently, the pressure whichthe springs exert against the pivoted arms may be varied by adjustingthe screws 62 and the screws may then be locked in place by means oflock nuts 63. While I prefer to yield ingly press 'therollersagainst theconverging faces of the standard, yetit is also possible to 'omit thesprings 61 and make the screws 62 long enough to bear directly againstthe swinging arms.

The soft fn'ction material on the rollers such, for example, as theO-rings 51 prevent marring of the standard and also help to resist theinward pull of the grinder carriage toward the front edge of the knifewhen the carriage reaches the lower portion of its travel. By means ofthe pivotal mounting'of the arms which support the rollers and by'providing means'for adjusting'the axes about which these arms swing, themechanism can be used on standards of various thicknesses and angles ofconvergence. By means'of 'the adjusting screws 62, the pressure exertedby the roller against the converging surfaces of the standard may bevaried in accordance with th amount of pull of the grinding belts on thecarriage, w ch in turn depends upon the amount of pressure exerted bythese belts on the knife.

The structure describedhas been found very useful in prolonging theusefullife of kniveson machines of this kind.

It will be understood that various changes in the details, materials andarrangements of parts which have been herein described and illustratedin order to explain the nature of the invention, may be made by thoseskilled in the art within the principle and scope of the invention, asexpressed in the appended claims.

I claim as my invention:

1. In a knife sharpening mechanism for cutting machines having a base, astandard extending upwardly from said base, a knife guided forreciprocal motion along said standard and projecting forwardlytherefrom, said standard having upright faces converging forwardlytoward the edge of said knife, power-operated knife reciprocatingmechanism mounted on the upper end of said standard, and a' grindercarriage movable to and fro along the knife edge and having knifesharpening elements mounted thereon, which move relatively to the knifein a direction to urge said carriage toward said knife, that improvementwhich includes rollers mounted on said carriage in position to engagesaid converging faces of said standard, and means for yieldingly urgingsaid rollers into engagement with said converging faces.

2. In a knife sharpening mechanism for cutting machines having a base, astandard extending upwardly from said base, a knife guided forreciprocal motion along said standard and projecting forwardlytherefrom, said standard having upright face converging forwardly towardthe edge of said knife, power-operated knife reciprocating mechanismmounted on the upper end of said standard, and a grinder carriagemovable to and fro along the knife edge and having knife sharpeningelements mounted thereon, which move relatively to the knife in adirection to urge said carriage toward said knife, thatimprovement'which includes rollers having resilient faces to engage theconverging faces of said standard, arms on which said rollers arerotatably mounted, means for pivotally mounting said arms on saidcarriage, and means reacting against said carriage and said arms forpressing said rollers into engagement with said converging faces.

3. A knife sharpening mechanism according to claim 2, characterized inthat said means include springs bearing against said arms.

4. In a knife sharpening mechanism for cutting machines having a base, astandard extending upwardly from said base, a knife guided forreciprocal motion along said standard and projecting forwardlytherefrom, said standard having upright faces'converging forwardlytoward the edge of said knife, power-operated knife reciprocatingmechanism mounted on the upper end of said standard, and a grindercarriage movable to and fro along the knife edge and having knifesharpening elements mounted thereon, which move relatively to the knifein a direction to urge said carriage toward said knife, that improvementwhich includes parts mounted onsaidcarriage and extend ingt to iniity tosgidconverging faces of said, standard in opposite directions, androllers mounted on said parts and engaging said converging faces toresist movement of said carriage toward said knife edge, said rollershaving resilient surfaces engaging said converging faces of saidstandard.

5. In a knife sharpening mechanism for cutting machines having a base, astandard extending upwardly from said base, a knife guided forreciprocal motion along said standard and projecting forwardlytherefrom, said standard having upright faces converging forwardlytoward the edge of said knife, power-operated knife reciproeatingmechanism mounted on the upper end of said standard, and a grindercarriage movable to and fro along the knife edge and having knifesharpening elements mounted thereon, which move relatively to the knifein a direction to urge said carriage toward said knife, that improvementwhich includes a pair of arms mounted on said carriage at opposite sidesof said standard and extending toward said converging faces of saidstandard, rollers mounted on said arms forengagement with saidconverging faces for opposing movement of said carriage toward saidknife, and means for adjusting said arms relatively to said carriage andto said converging faces to provide correct bearing of said rollers onsaid faces.

References Cited in the file of this patent UNITED STATES PATENTS1,815,018 Wagner July 14, 1931 2,060,197 Greenbaum Nov. 10, 19362,183,788 Clark et a1 Dec. 19, 1939 2,371,492 Wultf Mar. 13, 19452,563,921 Clark Aug. 14, 1951

